.main_box {
    position: absolute;
    text-align: center;
    margin-top: 20px;
}

body {
    background-color: #2D323C;
}

.picture_piece {
    width: 24%;
    min-width: 300px;
    margin: 5px;
    float: left;
    position: relative;
    display: block;
    padding: 13px 13px 0 13px;
    background: #fff;
}

.picture_piece img {
    width: 100%;
    height: 100%;
}

.pic_box {
    max-width: 100%;
    max-height: 100%;
    object-fit: cover;
}

.txt_box {
    font-size: 25px;
}